The separation of isotopes in the gas phase and, especially, uranium isotopes for uranium enrichment, based upon different molecular weights and/or different kinetic cross sections of the molecules of the isotopes to be separated in the gas phase, can be carried out by the separating-nozzle process well documented in the literature and described in the aforementioned copending application and the art cited therein.
The gas mixture, in this system, is forced with or without a carrier (low-molecular-weight gas) through slit-like nozzles, the outflow of which is intercepted by skimmer-diaphragm arrangements which separate the molecules of the heavier isotope from those of the lighter isotope.
The assemblies of such nozzles and associated skimmer diaphragms are referred to hereinafter as separating-nozzle units or, more generally, as separating units.
As described, inter alia, in the aforementioned copending application, it is common practice to feed each such separating-nozzle unit with a respective compressor and to connect the unit in cascade with other units for maximum resolution or separation efficiency. The latter application, moreover, describes arrangements wherein at least part of the compression heat is removed from the gas by a cooler upstream of each unit.
Separating-nozzle units, their principles and the various auxiliary devices (e.g. compressors) used with these units, are described in the following publications:
U.S. Pat. No. 3,362,131; PA0 U.S. Pat. No. 3,708,964; PA0 U.S. Pat. No. 3,877,892; PA0 German Pat. No. 1,052,955; PA0 German Pat. No. 1,096,875; PA0 German Pat. No. 1,198,328; PA0 German Pat. No. 2,031,687; PA0 CHEMIE-INGENIEUR-TECHNIK, Vol. 29, pp. 365 ff. (1957); PA0 CHEMIE-INGENIEUR-TECHNIK, Vol. 39, pp. 1 ff. (1967); PA0 ATOMWIRTSCHAFT/ATOMTECHNIK, Vol. 13, pp. 359 ff. (1968).
As described in the aforementioned application, a plurality of separating-nozzle units can be functionally integrated into a separating cascade with the aid of a vacuum-tight vessel having a circular-plan configuration and internally subdivided by radial partitions into sectors for the respective cascade stages. The gas ducts can be arranged centrally in the sectors in the upper part of the vessel and as connecting passages between the compressors, the coolers and the central gas passages.
Prior to this development and in most applications of the process, the apparatus was also functionally integrated into a separation cascade although the devices of the latter were usually not structurally integrated. The common practice was to provide the separating stages next to one another and to connect them by gas ducts which could be provided with enveloping or surrounding ducts to limit the possibility of escape of gas in the event of a failure in the system. This had various disadvantages especially with respect to the large spatial requirements of a row of stages, the distances between such stages made necessary by the disposition of the compressors between them, and the bulk of individually housed separating-nozzle units.
This resulted in:
(a) long supply and feed lines for gas, cooling water and electrical energy; PA1 (b) a large number of control, monitoring and measuring units and locations; PA1 (c) high instrumentation and monitoring costs; and PA1 (d) high capital cost, expensive transportation requirements for the numerous units and subassemblies, and considerable assembly and erection cost at the plant site.
Since all units and subassemblies of the apparatus had to be sealed vacuum-tight against atmospheric pressure, the numerous failure-prone weld seams necessary to this end created problems and required high weld-testing costs.
All of these disadvantages were reflected in the high capital and operating cost of uranium enrichment by the separation-nozzle process.
While the system described in my prior above-identified application was free from the last-mentioned disadvantages, work with this system has shown that it is capable of improvement. More particularly, the system of that application is characterized by an upright cylindrical column with a bottom portion, middle portion and upper portion. Radial partitions subdivide the interior of the column into sectors in the region of the central portion of the column and into chambers above and below these sectors. The arrangement was so constructed that the separating-nozzle units were located at outer portions of the sectors, the coolers in chambers below the separating element units and the compressors in the bottom portion of the column. The gas passages ran, on the one hand, centrally to the sectors as well as in the upper portion of the column and, on the other hand, as connecting ducts between the compressors, the coolers and the central gas passages. This has been found to be capable of simplification especially when large gas throughputs are desired.